Countermeasure systems are employed by military vessels to confuse or otherwise frustrate the targeting systems of an approaching missile or similar threat. Countermeasure devices, such as flares, chaff, acoustic emitters, IR emitters, and the like, are deployed to present a false image (i.e., decoy) of the vessel to these targeting systems. The false image is presented so as to draw the threat toward the false image and, therefore, away from the actual vessel. The false image manifests sufficiently far from the actual vessel so that damage caused by the threat when it strikes the decoy is mitigated or avoided all together.
Conventional countermeasure systems utilize arrays of cartridges, each of which carries one or more countermeasure payloads. As part of a representative launch sequence for such a cartidge, a firing circuit provides a first electrical signal to an excitation coil located in the bottom of the launch tube of the cartridge. The energized excitation coil induces a flow of current in a firing coil that is operatively coupled with a chemical-propellant charge. The excited firing coil initiates the ignition of the chemical-propellant, which generates an explosive force that propels the cartridge to its deployment position.
The ignition of the chemical-propellant charge simultaneously initiates a delay timer, which may be either a pyrotechnic delay or an electronic fuse. This delay timer enables the delayed ignition of a bursting charge contained within countermeasure payload. This enables the payload to be deployed appropriately when the cartridge reaches its desired deployment position.
Countermeasure deployment systems known in the prior-art have limited effectiveness against relatively sophisticated sensor platforms, however. This is due to the fact that the ignitions of the chemical-propellant engines used in a conventional countermeasure system emit characteristic launch signatures that have thermal, aural, and visual aspects. In particular, these signatures include a thermal bloom, a cloud of smoke, noise, a thermal trail and a smoke trail. In many cases, the thermal bloom heats the area immediate to the launch area, which results in a residual local thermal signature.
An electromagnetic countermeasure launcher has been developed that, among other things, has little or no launch signature. This electromagnetic countermeasure launcher is described in detail in U.S. patent application Ser. No. 11/535,480, filed Sep. 26, 2006, of which the instant application is a continuation-in-part. By replacing the chemical propulsion system of the prior-art with an electromagnetic propulsion system, however, the means for initiating the delay timer used to ensure proper countermeasure deployment is eliminated.
In order to induce an electric current in a firing coil or activate an electronic fuse, a conventional dedicated firing circuit could be included in the electromagnetic countermeasure launcher. The inclusion of such a circuit, however, reduces overall system reliability, increases control complexity, and add infrastructure cost.
Alternatively, a firing coil or electronic fuse can be initiated by means of an accelerometer in each cartridge. Each accelerometer would sense the acceleration associated with the launch of its cartridge and energize its associated delay timer. Unfortunately, a warship is subject to many sources of shock and vibration (e.g., explosions, collisions, etc.) that could be mistakenly interpreted by the accelerometer as an acceleration associated with payload launch. As a result, this approach increases the possibility of accidentally deploying a payload too early or of launching a payload that will not deploy properly.